Phytophthora Diseases of Greenhouse Tomatoes

Ilieva, E. Maritza Institute for Vegetable Crops, 32 Brezovxko shosse str., Plovdive-4003, BULGARIA

Species of Phytophthora caused a serious disease problem in many of tomatoes' growing greenhouse in Bulgaria. During last years observations were made on tomato plants, growing in 34 greenhouses in different parts of the country. Many Phytophthora isolates were obtained from tomato cultivars Eurostar, Anjella, Billi, Novi, Rosella, Precodor. According to the criteria of Waterhouse (1963, 1970), Novotelnova (1974), Stamps et al. (1990) 6 Phytophthora species were identified among 142 obtained isolates: P. capsici Leonian, P. cryptogea Pethybr, & Laff., P. drechsleri Tucker, P. erythroseptica Pethbr. var. erythroseptica, P. infestans (Mont.) de Bary and P. nicotianae Breda de Haan var. nicotianae (Table 1).

Phytophthora infestans causes the vary destructive and economically important blight disease usually in early autumn planted tomatoes. In this case conditions are favorable for sporangial formation and dispersal of P. infestans because on hot sunny autumn days greenhouses are not heated, and relative humidity is high and free water on the plant's surface is available after nights with lower temperatures.

Soil-borne Phytophthora species mentioned above caused damping off, root rot and stem rot of young tomato plants. Only P. nicotianae var. nicotianae was observed to cause fruit rot by natural infection. This fruit rot differs from that caused by P. infestans the soft consistency of infected fruits in the lower clusters.

P. nicotianae var. nicotianae is the most wide spread species of Phytophthora in the greenhouses in the country. All isolates of this species are of A2 mating type. The following wide spread species is P. cryptogea with both A1 and A2 mating types. P. capsici is presented by A1 mating type isolates. Less distributed in the greenhouses were P. erythroseptica var. erythroseptica and P. drechsleri. P. drechsleri was isolated only from tomato plants growing in a greenhouse near to Sandanski - a town in the South-West part of the country. This is the first report of P. drechsleri as pathogen of tomato plants in Bulgaria.

Table 1. Phytophthora species on greenhouse tomatoes in Bulgaria

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Phytophthora species                    Isolates #    Mating type  
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1. P. nicotianae var nicotianae             114          A2 	   
2. P. cryptogea                              13        A1 & A2 
3. P. capsici                                 5          A1 	   
4. P. infestans                               5         	   
5. P. erythroseptica var. erythroseptica      3	   		   
6. P. drechsleri                              2	   		   
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Literature cited:

Novotelnova N.S. 1974. Phytophthora fungi L. 206 pp.

Waterhouse G.M. 1963. Mycological Papers No 92, 22 pp.

Waterhouse G.M. 1970 Mycological Papers No 122, 59 pp.

Stamps D.J., G.M. Waterhouse, F.J. Newhook, G.S. Hall 1990 Mycological papers No 162, 28pp.